1. Field of the Invention
This invention relates to toilet systems that treat flushed human wastes from a toilet or a urinal and more especially relates to systems that macerate the flushed human waste followed by a sterilization before discharge from the system.
2. Description of the Prior Art
Broadly speaking there are two general types, recirculating and nonrecirculating, of toilet systems that receive human body waste.
The recirculating toilet systems are particularly useful on airplanes. For these systems it is necessary to provide initially in a waste-receiving tank a limited amount of flush water. The flushed water flows into that tank. During each subsequent use filtered water is pumped to the toilet as flush water from the accumulated mixture of initial water and increasing content of human body waste. These recirculating toilet systems minimize the amount of flush water required to be added to the airplane at the start of a period of service of the toilet system in the airplane. Some systems of this type provide a periodic withdrawal from the tank of a part of the accumulated mixture of body waste and initial flushing water to another tank in which it is heated to evaporate part of the water content. The latter systems of this type are disclosed in assignee's U.S. Pat. Nos. 3,535,712 and 3,536,196. In these patents it is disclosed that this evaporation of part of the water content produces a slurry that can be incinerated. The incineration of the slurry to ash after the evaporation can be performed in the same tank when the heated tank etc. are suitably constructed.
In another recirculating toilet system, that is shown in U.S. Pat. No. 3,831,534, the accumulated mixture of initial flush water and human body waste is periodically transferred to an incinerator in which the liquid content is evaporated and discharged and the solids are converted to ash by a combustion flame.
A modified recirculating toilet system is disclosed in U.S. Pat. No. 3,733,617. In that system the human waste is macerated during transfer to a tank from which it is fed to a heated vacuum chamber in which volatile liquid of the waste is evaporated while the solids are withdrawn from the bottom as dehydrated waste. The evaporated liquid is condensed and that liquid is transferred to a vessel from which it is pumped to the toilet for the flushing of the toilet.
The nonrecirculating toilet systems are used in facilities including mobile vehicles, such as passenger railroad cars and marine units, that have available a source of flush water that is not limited as is the case for the recirculating toilet systems installed in airplanes. These toilet systems when installed, for example, in passenger railroad cars and marine units, do not have the capability of transferring the flushed human waste to a sanitary sewer system as is the case for those nonrecirculating toilet systems installed in homes. In the past the toilet systems in passenger railroad cars merely dumped the flushed waste along the railroad right-of-way during the travel of the train. In the case of marine units the human waste from toilet systems was dumped overboard without any treatment.
Various systems have been developed to treat the human waste before dumping it. One system, that is illustrated by U.S. Pat. No. 3,846,847, includes means to add a tablet to the flushed waste prior to its maceration. The macerated waste is transferred to a decontamination tank. The tablet provides a chemical decomposition of the waste. The product is dumped. In the marine toilet system of U.S. Pat. No. 3,699,592 flushed human waste is macerated and chemically treated before dumping overboard.
The addition of a chemical tablet or fluid to the flushed waste requires equipment to dispense the chemical during the transfer operation and it is necessary to ensure that the supply has not been depleted. Chlorination has been used to destroy bacteria prior to discharging the macerated flushed waste from the toilet system. The chlorination is not totally effective for the treatment of human waste containing solids and it does not necessarily kill the spores and viruses. Of course, it is desirable to avoid handling of chlorine tanks for their connection into a toilet system for treating human waste.
Instead of a chemical treatment of the entire flushed waste the toilet system described in U.S. Pat. No. 3,548,421 provides a separation of the flushed waste to provide a solid waste matter that is incinerated and a liquid that is subjected to a chemical treatment. In toilet system of U.S. Pat. No. 2,768,386 the flushed waste is homogenized and then transferred to an incinerator in which the liquid content is volatized and discharged to the atmosphere and the solids are incinerated in the same operation.
Assignee's U.S. Pat. No. 3,787,901 claims a toilet system in which the flushed human waste is macerated and then transferred to a storage tank in which the macerated waste is heated to evaporate water for a volume reduction of the waste. In the event that it is desired to treat the resultant concentrated flushed waste at the site of the toilet system, the toilet system further includes an incinerator to which the concentrated flushed waste is transferred for its conversion to gas and solids.
The most pertinent toilet systems of the nonrecirculating type are those described in U.S. Pat. Nos. 3,395,799, 3,396,410 and 3,546,713.
In the marine toilet system of U.S. Pat. No. 3,395,799 the flushed waste is passed through a triturator in which the solid particles of the waste are finely ground and then the flushed waste is transferred to a tank in which it is heat-treated at a predetermined temperature for a predetermined time before being discharged. The patent teaches that the heat treating is continued at a temperature of at least 140.degree. F. for a period of at least 30 minutes.
In the toilet system of U.S. Pat. No. 3,396,410 the flushed waste is discharged from the toilet to a tank. When sufficient flushed water is accumulated in the tank, the waste will be recirculated through a heating zone until the waste in the zone reaches a temperature that causes a valve to open. It is stated that this temperature is sufficient to destroy or neutralize harmful bacteria. Then the liquid waste is transferred from the tank through the valve until the level of flushed waste in the tank falls to the level at which recirculation and heating cease. When sufficient additional flushed waste has been added to the tank, heating and recirculation resume.
In the toilet system of U.S. Pat. No. 3,546,713 flushed waste from a toilet is macerated and pumped to a storage tank where it is accumulated until the height of the flushed waste rises to a level at which it actuates a level sensor mounted in the lower portion of the storage tank. At this level the flushed waste in the storage tank has a volume at least equal to the capacity of a smaller treatment tank. The energization of the level sensor initiates the operation of a pump between the two tanks. Before the level in the storage tank is lowered to a level in which the level sensor is no longer energized a sensor in the bottom of the treatment tank is operated by the initial portion of waste transferred to the treatment tank from the storage tank so that the pump continues to operate. Adjacent the top of the treatment tank there is another level sensor that is operated by the transferred flushed waste in the treatment tank when it rises to that level. That sensor, when operated, stops the operation of the pump transferring flushed waste from the storage tank to the treatment tank. The treatment tank is adapted to contain a much smaller quantity of waste than the storage tank can contain. The treatment tank is provided with a heater that is turned on when the pump operation is initiated. A temperature responsive sensor is positioned in the treatment tank and it operates when the temperature of the flushed waste in the tank reaches a relatively high predetermined temperature, for example, 300.degree. or 350.degree.. when the temperature sensor is energized upon attainment of the predetermined temperature, it turns off the heater and initiates the operation of a pump for removal of treated flushed waste from the treatment tank. That pump continues to operate until the sensor at the bottom of the treatment tank is no longer energized by flushed waste in the treatment tank.
In the system of U.S. Pat. No. 3,546,713, a cycle, of transfer of waste from the storage tank to the treatment tank, of heat treatment in the latter tank and then discharge from it, is repeated so long as the level of flushed waste in the storage tank is above the minimum level as determined by the level sensor in the storage tank. The treatment tank is connected at its top to a safety valve that connects with a vent line extending from the top of the storage tank to a discharge opening in the wall of the side of the boat in which the marine toilet system is installed. This safety valve is normally closed and is opened only when the anticipated maximum operating pressure in the treatment tank is exceeded. A check valve is in a line between the treatment tank and the pump that transfers flushed waste from the storage tank.
The toilet system disclosed in U.S. Pat. No. 3,734,852 heat treats flushed waste. The waste is elevated to a temperature of at least the boiling point of water. Control means is provided for retaining the waste in a heat-treatment means for a sufficient period of time at an elevated temperature whereby the bacterial count of the waste is reduced to a tolerable level. In the system the flushed waste is transferred from a holding tank to the heat-treatment means that includes a heated chamber through which the waste is moved by a rotating screw while being heated to the temperature of at least that of boiling water. The speed of the screws is controlled so that the retention time of the waste is subjected to sufficient heat to substantially destroy all of the bacteria so that the baterial count is no more than the low tolerable level. The construction may also include a valve that prevents the waste from being discharged from the heat-treatment means by the screw until the temperature of the waste is at least at the boiling point of water.
The patents mentioned above are illustrative of the prior art of toilet systems. There may be other more pertinent art.